Usually, if humidity is right, a snake will shed all in one piece in a matter of minutes. They start with the head and then crawl out of the old skin, leaving it inside-out - kind of like taking off a wet sock. If it's been 24 hours and only part of the skin has come off, give Amy a soak for about 15 minutes, then let her crawl through a damp towel. That'll help loosen up and get rid of the old skin. Do not try to peel off the old skin, especially if it's dry.

I'm not sure how long you've had Amy. One of our snakes had a bad shed right after we got him because the pet store had not kept the humidity up at all. Since then, it's been one perfect shed after another. Make sure the hygrometer you're using is digital, not analog. The analogs are SOOO inaccurate.